Pulse transformer



Dec. 9, 1969 CLARK E fAL PULSE TRANSFORMER 2 Sheets-Sheet 1 Filed Jan. 15, 1968 FBG. 2

410+ 44010 FIG. 3

INVENTORS KENDALL CLARK RUDOLPH F. LIA

K CLARK ET AL Dec. 9, 1969 PULSE TRANSFORMER 2 Sheets-Sheet 2 Filed Jan. 15, 1968 United States Patent 3,483,497 PULSE TRANSFORMER Kendall Clark and Rudolph F. Lia, Poughkeepsie, NY assignors to International Business Machines Corporation, Arrnonk, N.Y., a corporation of New York Filed Jan. 15, 1968, Ser. No. 697,955 Int. Cl. HOlf 27/02 US. Cl. 336-96 22 Claims ABSTRACT OF THE DISCLOSURE The windings and connecting leads for a pulse transformer, particularly of the pluggable variety, are produced by the die casting of metal to form the windings and leads. A plastic housing or casing made of insulating material serves in part as the die for forming the windings and connecting leads. Terminal pins are inserted into specially formed slots and the pins are interconnected with the aforesaid connecting leads in the die casting operation.

BACKGROUND, SUMMARY AND OBJECTS OF THE INVENTION This invention relates to an improvement in the manufacture of ferromagnetic devices and, more particularly, to the fabrication of extremely small, annular bodies or cores having suitably dispossed windings and adapted for use in pulse transformers, memory elements, and the like.

The present invention is more particularly concerned with the fabrication of inductors and transformers comprising torodial cores, usually composed of ferrite material, surrounded by windings. The invention is also concerned with a technique for so fabricating these devices that they are immediately ready for application, in the form of pulse transformers and the like, in electrical circuits. More specifically, they are made ready for installation in the form of so-called pluggable units.

When magnetic cores are to be utilized in typical application, such as in pulse transformers, and other applications, the need arises to preserve the integrity of the cores; particularly, to prevent damage to any of their magnetic properties while turning them out at an extremely high production rate. A tremendous demand, of course, exists for great numbers of core units or assemblies, which may run into the millions of units in typical computer installations. One of the important forms for these core units is a pluggable unit which is designed to include a plurality of terminal pins extending from the casing or housing and connected with the core windings.

Accordingly, the present invention envisions a technique for the fabrication of conductors and transformers comprising toroidal cores, whereby such devices are producible in great numbers by the integral die casting of the windings and connecing leads therefor. The technique also includes the die casting of metal to surround the terminal pins. As as result, following the die casting operation the pluggable units are immediately ready for use in electrical circuits.

In order to provide a man skilled in the art with some background for gaining a thorough appreciation of the present invention and in order to highlight the salient differences which characterize the present invention, references may be made to US. Patent 3,319,207. This patent discloses a magnetic component basically comprising a grooved toroidal ferrite body including a metal filling provided in the grooves so as to define a helical winding for the toroidal body. In other words, the etal follows the grooves in spiral fashion so as to completely surround the toroidal core. Other patents that may be referred to as providing additional background are US. Patents 2,965,- 865, 2,512,162 and 2,654,861.

The essential technique for US. Patent 3,319,207 cited above has as its fundamental objective the provision of an improved magnetic component in which the winding or coil for the magnetic core does not have to be produced by conventional winding operations which are normally required when ordinary wire is used to form the coil. Although the technique described in this patent obviates the requirement that the coil be laboriously wound, answers are not provided for developing a high production approach to forming the magnetic core units. In other words, the described technique leaves unfulfilled the objectives of achieving a significant reduction in the handling of magnetic cores, while accomplishing the necessary encapsulation, formation of windings and interconnections, and formation of terminals or pins for the connection of the cores to circuit modules or the like.

Accordingly, it is a basic object of the present invention to reduce significantly the handling operations that have normally been required in the manufacture of annular magnetic cores, adapted for use in pluggable types of pulse transformers and like devices.

Another basic object is simultaneously to form the windings for the magnetic core and to place the core in a rigid package.

A further object, is to have the package or housing itself constitute part of the means for forming the aforesaid windings and interconnections.

Briefly stated, the present invention provides a winding construction and an associated encapsulation method which produces transformers, and like devices, disposed within a package, in the form of a plastic case or housing, such that the plastic case assists in the fabrication of the windings and assures that they are locked in place. The windings, interconnections and terminal pins that are required for the transformers are all formed simultaneously by a die casting operation. In this die casting operation, the die that is used is formed partly of steel or the like, while part of the die is constituted by portions of the plastic case. By this arrangement the windings as they are fabricated to surround the core are in profile, i.e. they extend beyond the limits of the core body. In other words, the core body including the insulation immediately surrounding the core, has a certain fixed boundary defined by smooth or unbroken peripheral surfaces. The windings, as these are created, extend beyond the peripheral surfaces of the core body.

In addition to the simultaneous formation of the required windings and interconnecting leads, it is a further feature of the persent invention that the required terminal pins are provided as die cast inserts. In other words, the inserts are set into the die when the windings are to be formed and these inserts become locked into specially formed slots within the plastic case or housing.

Recapitulating, the essence of the technique of the present invention may be considered as comprising the steps of simultaneously forming the windings in profile around an annular core body, forming these windings so that they are locked into a plastic case or housing which partly defines the die, whereby the entire core body or unit is firmly supported.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES lA-lF are perspective views illustrating a number of steps in the fabrication of a magnetic core pulse transformer or the like in accordance with the present invention.

FIGURE 2 is a sectional view taken through the die casting apparatus and showing the magnetic core unit which is about to be inserted for the die casting operation.

FIGURE 3 is another sectional view of the die casting apparatus showing such apparatus in the closed position, the magnetic core unit having been inserted therein.

FIGURE 4 is a bottom plan view of a typical magnetic core unit.

FIGURE 5 is a sectional view taken on the line 55 in FIG. 4.

FIGURE 6 is another sectional view taken on the line 66 in FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now particularly to FIGURES 1A and 1B, there is shown here a typical magnetic core unit which is to be fed to a die casting apparatus. The magnetic core unit 120 consists of an annular ferrite core 100 completely surrounded by an adherent insulating covering 110. This insulating covering is necessary because the ferrite core material that is generally used is a conductor and it is therefore necessary to insulate the core from the windings that are to he placed around it.

A plastic housing or case 130, seen in FIG. 1C is provided for insertion with the core unit 120 at the die casting apparatus. This plastic case 130 has been specially molded and has suitably disposed grooves 131 formed at spaced locations denoted 130a, 1301) and 1341c at the inner periphery of the case 130. The case is also provided with a number of keystone shaped slots 133 at one end thereof. The purpose of the grooves 130:: is to define, in the die casting operation, openings or recesses for reception of metal used to form parts of the windings for the core, while the purpose of the slots 133 is to receive the pins 132 and the metal which surrounds them, and thereby to lock the pins in place.

For the purposes of the present invention it has been found that a thermosetting plastic is the most preferred type of material for the case 130 which serves as the package for the magnetic core unit 120. Such a thermosetting plastic material will not be deleteriously affected by the die casting operation that is to be performed with the present technique.

Referring now to FIGURES 1D, 1E and IF, there will be seen several stages in the processing of the core unit 120. In particular, FIGURE 1D shows the assembly of the plastic case 130, the core unit 120 and the pins 132. As will be explained, these elements are integrally combined in the die casting operation. The core unit is disposed within the plastic case 130 so that its outer peripheral surface abuts the inner peripheral sections of the case designated 130a, b and 0, whereby the series of spaced grooves 131 in these sections are immediately adjacent the outer periphery of the core unit 120. The pins 132 are shown in position with their ends within the slots 133. This assembly of FIGURE 1D represents the condition at which the die casting operation is about to be performed in the die casting apparatus of FIGURE 2.

Referring now to that figure, the core assembly is shown in the middle of the figure, the parts 140a and 14017 of the die being separated. Each of the parts 140a and 140b contains a passageway 142a and 1421: respectively for receiving the metal from appropriate conduits, the metal being forced at the proper time into these passageways and then into the channels and recesses within the die. It will, of course, be appreciated that the die parts 140a and 140b have their surfaces precisely formed to produce the desired winding configurations for the core unit 120. As will be understood a great variety of winding configurations can be obtained for the core unit 120. However, regardless of the particular winding configurations that is selected, the general objective in all instances is to define a helical winding or windings surrounding the core unit 120 and, at the same time, to provide the appropriate interconnection leads therefrom out to the ter- 4 minal pins 132 at the edge of the plastic case 130. In pro ducing the helical winding or windings, the grooves 131 in the plastic case 130 define certain of the axially extending outer peripheral portions while the die itself defines the remainder of these required portions. The series of radially extending grooves 144a on the upper mold part 140a and the corresponding series of grooves 144b on the lower mold part 14017 serve to define the skewed portions of the windings, that is, those that extend along the radial plane surfaces of the core unit 120. Thus it will be appreciated that the grooves 144a and 14411 serve to define all of the upper and lower skewed portions 200x of the windings 200, as seen for example in FIGURE 1E. Correspondingly, the axially extending grooves 146a of the upper mold part meet and align with the corresponding grooves 14611 of the lower mold part 1401) and thereby serve to define the axially extending portions 200y of the windings 200 at the inner periphery of the core. The series of grooves 148b in the lower mold part define the remaining outer peripheral, axially extending portions of the windings, that is, those not defined by the grooves 131.

The aforementioned definition of the windings 200 by the grooves which are adapted to receive the die cast metal, can be appreciated in greater detail by reference to the bottom plan view of FIGURE 4, wherein there will readily be seen the serial connection of the skewed portions 200x at the top and bottom radial faces of the core unit and the axially extending portions 200;) to form the helical windings shown. The dotted lines for the portions 200x represent the upper radially extending portions of the several windings.

In addition to the formation of the windings 200 by reason of metal being forced into the aforedescribed grooves in the plastic case in the recesses in the die parts 140a and 140b, the interconnecting leads 220 are also formed by reason of the fact that suitable recesses or channels 210 are provided that connect with the winding pattern of grooves. These channels 210 connect respectively with the slots 133 provided in the plastic case at one end thereof.

In the actual die casting procedure, a succession of core assemblies comprising the plastic case 130, the core unit 120 and the terminal pins 132 are placed in the die and they are indexed therein by suitable means not shown. Although for the sake of clarity and simplicity only a single unit die is shown in FIGURE 2 it will be understood that multiple unit die casting apparatus can be utilized whereby vast numbers of core assemblies can be fabricated simultaneously.

The die is shown in the closed position in FIG. 3, the two heated sections or parts a and 14% having been clamped together. Also, another die part 140c is clamped together with the other parts of the die and serves to retain the pins 132. The die is usually heated to a temperature of approximately 440 F., depending on the metal used. A tin silver alloy was found to be the best composition in the fabricating of core windings. The percentage of silver was varied from about 5% upward to about 15%. The terminal pins which are in the form of die cast inserts are made of silver plated copper.

The metal in the form of the aforenoted tin-silver composition is injected into the die by means of the movable conduits 410 and pressure is applied so as to result in forcing this tin-silver composition into the grooves, recesses and channels, as already described, which define the various windings and interconnecting leads. Thus, the metal is forced into the grooves 131 at the inner periphery of the plastic case and into all the grooves in the die surfaces used for defining the windings for the core. Likewise, the metal flows through the channels 210 and into the slots 133 so as to surround the ends of the pins 132 which are held in these slots, the metal portion 142a is trimmed off. The resultant unit or assembly which is removed from the die casting apparatus is seen in FIG. 1E. It has all its essential elements connected by virtue of the die-casting operation such that the unit is now almost ready to be placed into service. It should be noted that in the illustrative embodiment depicted, the core unit 120 is situated approximately midway of the depth dimension of the plastic case 130. The core unit is effectively locked in place in this location and is not easily moved about. However, there are blank spaces, as can be seen, within the interior of the case 130. It is desirable to fill in these blank spaces and for this purpose a suitable filler material is used in all of the blank spaces, thereby maintaining' the core in a packed state.

In order that the finished pluggable transformer unit may be adapted to incorporation in circuit boards or modules, the stand-off projections 430 are provided at the pluggable end of the unit.

Although the finished unit as seen in FIG. 1F, and also, in FIGS. 4, 5 and 6 is provided with six terminal pins and with six associated interconnecting leads, this is merely one example of a unit that may be fabricated in accordance with the present technique. It will be understood by those skilled in the art that the windings and interconnections and pin arrangements may be greatly varied.

A second embodiment comprises a pulse transformer structure wherein the insulation 120 of core 100 is formed as a continuum of the case 130 by using the core 100 as an insert in the plastic mold during the molding of case 130, to the configuration of FIG. 1D.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiments, it will be understood that various ommissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art Without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An electrical component comprising an annular body, including an annular magnetic core surrounded by an adherent insulative coating, the periphery of said annular body being defined by completely smooth surfaces; a plastic case surrounding said annular body and having at its inner periphery a portion containing a plurality of spaced grooves, said portion contacting only the outer periphery of said annular body, said grooves containing metal so as to define in part at least one helical Winding around said annular body, and a separate encapsulant Within said casing and surrounding the remainder of said annular body.

2. The pulse transformer of claim 1 wherein said plastic case is a continuum of said insulative coating.

3. An electrical component comprising an annular body, including an annular magnetic core surrounded by an adherent insulative coating, the periphery of said annular body being defined by completely smooth surfaces; at least one helical winding surrounding said annular body and being defined by metal conductors; a plastic case having spaced inner peripheral portions, each having axially extending grooves contacting only the outer periphery of said annular body, portions of the metal conductors being disposed in said grooves, and a separate encapsulant within said casing and surrounding the remainder of said annular body.

4. The pulse transformer of claim 3 wherein said plastic case is a continuum of said insulative coating.

5. An electrical component as defined in claim 3 in which said annular magnetic core is composed of ferrite material.

6. The pulse transformer of claim 5 wherein said plastic case is a continuum of said insulative coating.

7. An electrical component as defined in claim 3 further comprising terminal pins for connecting said component to an external circuit, the terminal pins being disposed in slots to one end of said plastic case; and interconnecting leads extending from said winding so as to connect with the terminal pins in said slots.

8. The pulse transformer of claim 7 wherein said plastic case is a continuum of said insulative coating.

9. A pulse transformer comprising an annular body, including an annular core completely surrounded by an inherent insulative coating, the periphery of said annular body being defined by completely smooth surfaces; a plastic case surrounding said annular body and having at its inner periphery a plurality of spaced grooves contacting only the outer periphery of said annular body, said grooves containing metal so as to define in part the helical windings for said annular body, the windings extending around said body to define a primary and a secondary for said transformer, and a separate encapsulant within said casing and surrounding the remainder of said annular body.

10. The pulse transformer of claim 9 wherein said plastic case is a continuum of said insulative coating.

11. A pulse transformer comprising an annular body, including an annular magnetic core surrounded by an adherent insulative coating, the periphery of said annular body being defined by completely smooth surfaces; a plurality of helical windings surrounding said annular body and being defined by metal conductors; a plastic case having spaced inner peripheral portions, each having axially extending grooves contacting only the outer periphery of said annular body, portions of the metal conductors being disposed in said grooves, and a separate encapsulant within said casing and surrounding the remainder of said annular body.

12. The pulse transformer of claim 11 wherein said plastic case is a continuum of said insulative coating.

13. A pulse transformer as defined in claim 11, Wherein said annular core is composed of ferrite material.

14. The pulse transformer of claim 13 wherein said plastic case is a continuum of said insulative coating.

15. A pulse transformer as defined in claim 11, further comprising terminal pins for circuit connecting purposes disposed in slots at one end of said plastic case; and interconnecting leads extending from said primary and secondary winding so as to connect with the ends of said terminal pins in said slots.

16. The pulse transformer of claim 15 wherein said plastic case is a continuum of said insulative coating.

17. A process of fabricating an annular magnetic core so as to define a winding therefor, comprising the steps of disposing a plastic case in a die, said plastic case having a plurality of grooved portions at its inner periphery so as to provide recesses for receiving metal to define said winding,

placing the annular magnetic core in said die so that the grooved portion at the inner periphery of said plastic case contacts only the outer periphery of said annular magnetic core,

forcing the metal into the die so that the metal flows into the grooves, whereby the winding for said core is defined in part by the grooves, and the core is locked in place within said plastic case.

18. A process as defined in claim 17, wherein said die includes a series of grooves for defining the remaining parts of said winding.

19. A process as defined in claim 18, wherein said die further includes a plurality of channels for defining interconnecting leads from said windings to terminal pins.

20. A process as defined in claim 19, further including the step of inserting pins in slots at one end of said plastic case and forcing metal into said slots to connect said terminal pins with said interconnecting leads.

21. A process as defined in claim 20, wherein the die is heated to a temperature of approximately 440 F. and the metal for forming said winding and interconnecting leads is a tin-silver alloy.

22. A process as defined in claim 21, wherein said 3,251,015 5/1966 Denham 336-96 terminal pins are made of silver plated copper. 3,155,766 11/ 1964 Eichert et 21. L 33696'XR References Cited HENRY R. J ILES, Primary Examiner UNITED STATES PATENTS S. D. WINTERS, Assistant Examiner 2,818,514 12/1957 GoertZ et 211. 336-96 XR 2,899,631 8/1959 Cushman 336-96 XR Us CL 2,971,138 2/1961 MeiSel et a1 317-101 XR 3,146,332 8/1964 Keska 336-96 XR 29-606; 336-192, 200, 205, 229

3,246,287 4/1966 Benson 336-229 XR 10 

